Multiple lumen catheters which are surgically implanted into the body and used for dialysis are known, being disclosed in U.S. Pat. Nos. 5,405,320 and 5,509,897 to Twardowski et al. and U.S. Pat. No. 5,509,900 to Kirkman.
The multiple lumen catheters disclosed in '320 and '897 are three dimensional in form, specifically calling for catheter portions which are substantially perpendicular to remaining, planar portions. Such multiple lumen catheters have been promoted as being allegedly permanent devices providing access to a patient arteriovenous system for hemodialysis but have proven to have significant disadvantages. The three dimensional character of these catheters inherently serves to stress the vessels of the arteriovenous system in which the catheter resides, thereby shortening useful life of the catheter.
The catheter disclosed in '900 is intended and designed to be retained at a specific spot within a blood vessel by an anchoring tip which serves to retain the catheter with respect to the wall of the blood vessel. The anchoring tip, by fixing the catheter in place and not permitting relative movement of the vessel vis-a-vis the catheter, creates a potential for rupture of the vessel or for collection of thrombolytic material about the positioning means, both of which are undesirable.
With the increasing use of dialysis therapy and ever a increasing expected lives of dialysis patients, the need exists for a permanent dialysis catheter which can be surgically implanted within the patient's blood vessels, and causing minimum trauma to the patient on a continuing basis. The need further exists for such a catheter which minimizes the possible collection of thrombolytic material at the inlet and outlet orifices of the catheter while keeping the inlet and outlet orifices remote from the wall of the vessel in which the catheter resides, thereby promoting high flow hemodialysis with relatively low fluid pressures, resulting in minimal patient connection time to the dialysis machine, longer catheter useful life and reduced possibility of catheter dysfunction as a result of malpositioning.
Surgical cannulas or "sheaths" are typically utilized by medical personnel to establish transcutaneous access channels from a first percutaneous location to a second subcutaneous location. The access channel provides a conduit for the delivery of pharmaceutical products, removal of subcutaneous sample tissue and fluid, as well as the coaxial passage of instrumentation such as catheters and the like.
In surgical procedures which require only temporary use of a sheath conduit, "peel-away" style sheaths are utilized. The peel-away sheath has lines of weakness extending about opposing sides of its longitudinal length such that removal of the sheath can be accomplished by applying a separating force or "peeling" the wall sections downwardly from the transcutaneous end by way of integral pull tabs located thereon, to cause a linear tearing of the sheath material causing the "peeling" or failure of the A material. In this way, the sheath can be removed from the patient without removing the instruments positioned within the sheath channel.
However, application of the peeling force to the sheath wall sections tends to aggravate and/or enlarge the incision in the region of the sheath as force is applied downwardly into the incision. Stressing of the incision is particularly problematic in irregularly manufactured sheaths having uneven wall thickness along the lines of weakness. The wall thickness may also cause kinking when attempting to insert a product or device through its thin walls. Moreover, the peeling force tends to lift instruments within the sheath pathway upwardly from the patient.